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A block of mass m moves on a horizontal ...

A block of mass `m` moves on a horizontal rough surface with initial velocity `v`. The height of the centre of mass of the block is `h` from the surface. Consider a point `A` on the surface.

A

angular momentum about `A` is `mvh` initially

B

the velocity of the block decreases at time passes.

C

torque of the forces acting on block is zero about `A`

D

angular momentum is not conserved about `A`.

Text Solution

Verified by Experts

The correct Answer is:
A, B, D

(A) Angular momentum about `A` is `mvh` initially
(B) Due to friction velocity of block decrease with time
( C) Since angular momentum about `A` decreases so torque of forces is not zero about `A`
(D) Angular momentum is not conserved about `A`.
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Knowledge Check

  • STATEMENT-1: A block of mass m starts moving on a rough horizontal surface with a velocity v. It stops due to friction between the block and the surface after moving a certain distance. The surface is now tilted to an angle of 30^(@) with the horizontal and the same block is made to go up on the surface with the same initial velocity v. The decrease in the mechanical energy in the second situation is smaller than that in the first situation. because STATEMENT-2: The coefficient of friction between the block and the surface decreases with the increase in angle of inclination.

    A
    Statement-1 is True, Statement-2 is True, Statement-2 is a correct explanation for statement-1.
    B
    Statement-1 is True, Statement-2 is True, Statement-2 is NOT a correct explanation for Statement-1.
    C
    Statement-1 is True, Statement-2 is False.
    D
    Statement-1 is False, Statement-2 is True.

  • Asseration : A block of mass m starts moving on a rough horizontal surface with a velocity v. It stops due to friction between the block and the surface after moving through a ceratin distance. The surface is now tilted to an angle of 30^@ with the horizontal and same block is made to go up on the surface with the same initial velocity v. The decrease in the mechanical energy in the second situation is small than the first situation. Reason : The coefficient of friction between the block and the surface decreases with the increase in the angle of inclination.

    A
    If both Assertion and Reason are true and the Reason is correct explanation of the Assertion.
    B
    If both Assertion and Reason are true and the Reason is not the correct explanation of the Assertion.
    C
    If Assertion is true, but the Reason is false
    D
    If Assertion is false but the Reason is true.

  • In the following questions, each question contains Statement I(assertion) and StatementII(reason). Each questions has four choices a, b, c, and d out of which only one is correct. Statement I: A block of mass m starts moving on a rough horizontal surface with a velocity v. It stops due to friction between the block and the surface after moving through a certain distance. The surface is now titled to an angle of 30^@ with the horizontal and the same block is made to go up on the surface with the same initial velocity v. The decrease in mechanical energy in the second situation is smaller than that in the first situation. Statement II: The coefficient of friction between the block and the surface decreases with the increase in the angel of inclination.

    A
    (a) Statement I is true, Statement II is true, Statement II is a correct explanation for Statement I.
    B
    (b) Statement I is true, Statement II is true, Statement II is not a correct explanation for Statement I.
    C
    (c) Statement I is true, Statement II is false.
    D
    (d) Statement I is false, Statement II is true.

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